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65 APPENDIXES A THROUGH E UNPUBLISHED CONTRACTOR'S MATERIAL Appendixes A, B, C, and E submitted by the research agency are not published herein. Titles of available appendixes are as follows: APPENDIX A Summary of Agency Experiences APPENDIX B Historical Optimization-Based Approaches Used for Transportation-Related Problems APPENDIX C User's Guide for the Optimal Preventive Maintenance Timing Analytical Tool (OPTime) APPENDIX D Plan for Constructing and Monitoring Preventive Maintenance Test Sections APPENDIX E Example Illustrating the Inclusion of Different Cost Types Appendixes C and E are accessible on the web at http://trb.org/news/blurb_detail.asp?id=4306. The OPTime software in Appendix C can be copied on a CD-ROM for use. For a limited time, copies of Appendixes A and B will be available on a loan basis from the NCHRP. Appendix D is provided on the following pages.

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67 APPENDIX D PLAN FOR CONSTRUCTING AND MONITORING PREVENTIVE MAINTENANCE TEST SECTIONS INTRODUCTION OBJECTIVES The underlying premise of preventive maintenance is that The first step in developing an experiment is to identify the the application of treatments to a pavement in "good" con- objectives or goals of the preventive maintenance program to dition will provide some benefit above and beyond the per- help establish a link between the treatments selected for study, formance of the untreated pavement. It is further assumed the measures used to monitor performance, and the agency's that the benefit will vary, depending on the type of treatment, expectations. Goals might address pavement smoothness, when it is applied, and the condition of the pavement at the noise mitigation, accident reduction, and pavement life exten- time of application. However, because only a few agencies sion, for example. While the overall objective of the exper- have had long-term experience with preventive maintenance iment is to identify the best time to apply preventive main- practices, there is little evidence of these benefits. Attempts to tenance, the objective is inextricably linked to preventive track these benefits after the fact--by examining historical maintenance performance objectives. pavement performance data, for example--are problematic The types of treatments of asphalt and concrete pave- because of the absence of critical data, such as the condition ments that might be evaluated to achieve specific objectives of the pavement at the time of treatment application, the qual- are listed in Table D-1. While almost any treatment could ity of construction, and periodic observations of performance. extend pavement life, certain performance objectives would Contributing to the difficulties in documenting the bene- best be achieved with the application of specific treatments. fits of preventive maintenance is the lack of a strong connec- tion between the commonly used methods of monitoring EXPERIMENT DESIGN pavement performance and the types of benefits provided by preventive maintenance treatments. Preventive maintenance Perhaps the most important part of the plan is the design is often aimed at maintaining or improving functional per- of the experiment. An effective design ensures that the objec- formance while most condition surveys focus on a pavement's tives of the experiment are fully met. Test section sites are structural performance. selected to meet the immediate and long-term needs of the Perhaps the best way to evaluate preventive maintenance experiment. While concerns about constructibility and the effectiveness--and show when it is most effective--is through availability of local support for placing the test sections are monitoring specially constructed test sections. Properly recognized. Long-term needs include monitoring and data designed, constructed, and monitored test sections would gen- collection, and subsequent analyses of data. An underlying erate data appropriate for the pavement types, traffic loadings, consideration in locating a test section is to avoid possible environmental conditions, and maintenance treatments that confounding factors, such as variability in the pavement con- are typical of an agency's practices and conditions. dition that could impact the interpretation of the results. This appendix outlines the steps involved in creating a plan Some of the key items in the design are discussed in the for establishing preventive maintenance test sections that can following sections. be used to generate the information needed to implement a successful preventive maintenance program. Results from the experiment would be used to determine the benefits (or effec- Site Selection tiveness) of specific preventive maintenance treatments based on the age and condition of the pavement. An analysis using There are two major issues to consider in site selection: the methodology described in Chapter 3 can then be made to (1) limiting or avoiding confounding factors and (2) ensur- identify the optimal time to perform preventive maintenance. ing that applicable and useful results are obtained from the site. Confounding factors refers to variations in site condi- The steps in developing the plan include the following: tions that might later complicate the analysis of the data. Among such factors are non-uniform traffic volumes, cross · Identify objectives sections, and support conditions. The key to site selection is · Complete experiment design to consider the analyses that will be performed and control as · Construct experiment many of the factors that will affect them as possible. Under- · Monitor performance standing how the findings will eventually be used is another · Analyze results factor in obtaining useful results. For example, if the agency

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68 TABLE D-1 Relationship between performance objectives and preventive maintenance treatments Preventive Pavement Surface Type Maintenance Performance Objective Bituminous PCC Measure Improve Ride Slurry Seal Diamond Grinding IRI (Reduce roughness) Microsurfacing PSI Ultrathin Friction Course Thin Overlay Noise Control Ultrathin Friction Course Diamond Grinding dB Slurry Seal Microsurfacing Increase Surface Chip Seal Diamond Grinding Skid Number Friction Slurry Seal Mean Texture Depth Ultrathin Friction Course IFI Thin Overlay Extend Pavement Crack Sealing Joint and Crack Sealing Condition: Life Fog Seal Cracking Scrub Seal Patching Chip Seal Rutting Slurry Seal Raveling Microsurfacing Faulting Thin Overlay Pumping Ultrathin Friction Spalling Course Potholes Patching Reduce Moisture Crack Sealing Joint and Crack Sealing Condition: Infiltration Scrub Seal Cracking Chip Seal Patching Slurry Seal Rutting Microsurfacing Raveling Thin Overlay Faulting Ultrathin Friction Course Pumping Spalling Potholes Patching IRI = International Roughness Index; IFI = International Friction Index; dB = decibel maintains pavements in different environments, then produc- the performance of the overlay, and to that of the maintenance ing broadly acceptable results from sites constructed in one treatment, cannot be fully isolated. type of environment should be carefully considered. Similar consideration should be given to other relevant aspects of the site, such as pavement type, design, condition and age, and Pavement Design traffic level. The pavement should be of a uniform design over the length of the project. This means that all structural features Pavement Type (i.e., paving layers, materials, and thicknesses) and geomet- ric features (i.e., number of lanes) should be the same over Hot-mix asphalt (HMA), portland cement concrete (PCC), the length of the project. The subgrade should also be fairly and other bituminous-surfaced pavements are all candidates uniform over the project and free of swelling or frost sus- for inclusion in a preventive maintenance experiment. Test ceptible soils. sections should be constructed on the types of pavement for which preventive maintenance treatment applications will be evaluated. Pavement Condition and Age It is recommended that initial efforts be kept fairly simple by limiting pavement type to bituminous-surfaced or PCC Because pavement age is an indirect indicator of the pave- pavements that have not been rehabilitated or received any ment condition, a pavement that is fairly young (e.g., less than other blanket maintenance treatment. While it could be argued 5 years old) and still in good condition should be selected. It that an overlaid pavement will provide similar results for should not exhibit any signs of significant structural deterio- some of the objectives (such as noise mitigation or improved ration (such as rutting or fatigue cracking), and only small surface friction), the contribution of the original pavement to amounts of other types of distress (such as linear cracking or

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69 weathering/raveling) should be present. As with other factors, Ultimately, the selected treatments should match the it is also desirable that the condition of the pavement be fairly agency's preventive maintenance objectives. For example, if uniform over the length of the project and that any sig- an agency's objective is to maintain high levels of surface nificantly deteriorated areas not be included as part of the friction, then treatments that enhance surface friction should experiment. be evaluated in the experiment. Table D-2 summarizes some of the primary benefits provided by the different preventive maintenance treatments; this information would help in select- Traffic Levels ing treatments to support specific preventive maintenance objectives. Of course, several different treatments intended The traffic levels should be uniform over the project to elim- for different purposes cannot be studied in the same project. inate the effect of traffic variability on treatment performance. As part of the experiment, agencies may also include new Low to moderate traffic volumes (e.g., 1,000 to 5,000 vehicles materials or techniques or treatments with which they have per day) may be most appropriate for the experiment because little or no previous experience. they cover the conditions for which many treatments are used. While lower traffic volumes make it easier to monitor the performance, roadways with higher traffic volumes provide a Treatment Timing more severe test for the treatments. Higher traffic volumes also make it harder to monitor performance and may cause prob- In the experiment, the timing of the treatment application lems when the treatments fail and some form of rehabilitation will be varied so that the effect of treatment timing on per- is required. Also, it is important that adequate construction and formance (or effectiveness) can be evaluated. In this regard, performance records be kept not only to fully document the two critical issues must be considered: determining when the design of the project, but also to help assess the effects of the first treatment should be applied and determining how often various treatments on key performance measures. subsequent treatments should be applied. On a new pave- ment, a preventive maintenance treatment might be applied Treatment Selection before the pavement is opened to traffic (e.g., a fog seal appli- cation to bituminous surfaces) or shortly after construction The selection of preventive maintenance treatments for (e.g., 1 to 3 years). To evaluate timing issues, a number of evaluation in the project should be based on the specific goals untreated sections must initially be kept within the experi- of the agency's preventive maintenance program. The agency ment so that treatments can be applied at different times in must recognize that including different treatments will require the life of the pavement. For example, if a chip seal is applied a larger test site and will involve the collection of a large 2 years after construction, sufficient untreated test sections amount of data and the conduct of extensive data analysis. For must be available to allow chip seal application later (e.g., 3, each treatment included in the experiment, additional sections 4, 5, or 6 years). Applying the treatment at 1 year should also are needed for replicating, and multiple sections are needed be considered to determine if more benefit is obtained from for treatment applications at different times in the future. such an early application. TABLE D-2 Primary benefits of different maintenance treatments Life Moisture Treatment Roughness Friction Noise Extension Reduction Bituminous-Surfaced Pavements Crack Sealing X Fog Seals X Scrub Seals Slurry Seals X Microsurfacing X Chip Seals X Ultrathin Friction Course Thin Overlays PCC Pavements Joint and Crack Sealing X Diamond Grinding = Major effect x = Minor effect

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70 The actual timing of the treatments depends on the type N = Number of treatments to be evaluated. and purpose of the treatment. More substantial maintenance TC = Number of timing cycles per treatment. treatments (such as thin overlays) would require greater tim- R = Number of sections incorporating each treatment. ing cycles than a lesser treatment (such as a fog seal). Also, the timing cycles are influenced by other factors such as cli- For example, if four treatments are to be evaluated at three mate and quality of construction; some general guidelines are timing cycles (3, 6, and 9 years), and there are to be two sec- provided for various preventive maintenance treatments in tions per treatment (1 set of replicates), then the required proj- Table D-3. ect length is [457 × ((4 × 3) + 1)] × 2, or 11,882 m (38,980 ft). Some additional length may be needed for transitions between sections or to exclude certain areas (such as intersections or Site Layout bridges) within a project. It can be seen from the example that a test site can become One of the most important aspects of the site layout is its quite long rather quickly, so it is important that agencies care- length, it must be long enough to accommodate all the treat- fully select the number of treatments to evaluate. Of course, ments under consideration, including control (do-nothing) the replicate treatments could be placed in the opposing direc- and replicate sections. The site must be long enough to allow tion which would help shorten the required project length (but adding treatments to bare sections in subsequent years in potentially add a confounding factor because of different traf- order to address the timing issue. Specific items relevant to fic levels). the site layout are described in the following subsections. Section Length Project Length Each individual test section should be long enough not only The project must be long enough to accommodate all test to facilitate construction but also to provide a statistically sections. As a general rule, the required length of the project valid sampling of performance. With many of the treatments can be computed as follows: using equipment that requires some start-up calibration, shorter sections could have areas at their beginning and/or TPL = [TSL × (( N × TC) + 1)] × R (Eq. D-1) end that are not uniform in performance. At the same time, the section should be short enough to help contain the phys- where: ical size and costs of the experiment. A minimum section TPL = Total project length, m (or ft). length of 457 m (1,500 ft) appears to be reasonable, although TSL = Total section length, m (or ft) (457 m [1,500 ft] longer sections may be warranted in some instances. How- recommended). ever, the evaluation length does not need to be as long as the section length; a section evaluation length of 150 m (500 ft) is appropriate. TABLE D-3 Suggested treatment timing cycles Recommended Replicate Sections Year of Initial Treatment Treatment Treatment Timing Cycle The use of replicate sections as part of the design is strongly Crack Sealing 1 to 3 Annually recommended. Replicates are identical sections that are con- Fog Seals 0 to 3 Annually structed to improve the statistical validity of the analysis and Bituminous-surfaced Scrub Seals 2 to 6 Annually also to create "back-ups" if the original sections are taken out of service. On the other hand, while more replication improves Slurry Seals 2 to 6 Annually the reliability of the results it also increases the cost of con- Microsurfacing 3 to 7 2 years structing, monitoring, and analyzing the results. Although sev- Chip Seals 2 to 5 Annually to 2 years eral replicates makes it easier to break out anomalous behav- Ultrathin Friction Course 2 to 6 2 years ior and improve the statistical validity of the results, only one Thin Overlays 5 to 8 2 years set of replicates is recommended (that is, a total of two sections for each treatment/timing combination) to reduce cost. Joint and Crack Sealing1 4 to 102 surfaced 2 years PCC- It is also recommended that replicate sections be con- Diamond Grinding 5 to 10 3 years structed on the same roadway, end to end in the same lane, if 1 possible, but placed randomly within the project. If site con- Refers to joint resealing and crack sealing. It is assumed that if optimal timing of joint resealing is being evaluated, any cracks will be kept sealed. straints do not allow this layout, the replicates can be built in 2 Timing is somewhat dependent on the occurrence of cracking and/or the the opposing traffic lanes and placed randomly within the proj- need for resealing the joints. ect. For multi-lane roadways, replicates can either be con-

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71 structed at the end of the project or in the opposing lanes. For The duration of the experiment can be shortened, however, example, if chip seals, slurry seals, and thin overlays are con- based on regular analysis of the test results. For example, structed as three separate sections in the northbound lanes new treatments do not need to be applied and maybe perfor- of a roadway, replicate sections of the same three treatment mance does not need to be further monitored if it is clear that types can be constructed in the southbound lanes of the same the performance trend is declining. roadway. While it is possible to apply a treatment to both lanes in one direction of a multi-lane facility and use the sec- ond lane as a replicate, the different traffic level in the repli- CONSTRUCTION cate lane will introduce a confounding factor in the analysis. The most important construction concern is ensuring that test sections are properly constructed. This is best accom- Factorial Design plished by following best practice, project specifications, and the material supplier's recommendations. While this might Factorial designs are typically developed for such experi- seem like unnecessary guidance, there are any number of ments. These designs are often presented in a tabular form to research efforts that have been compromised by construction show what is being evaluated in the experiment in an easy- problems. The following subsections describe specific areas to-understand manner. A hypothetical example of a factorial where attention is needed to minimize or eliminate construc- design for a project that has been designed to last "n" years tion problems. is shown in Table D-4. Factorial design tables are an effec- tive way for agencies to lay out their experiment and quickly get an indication of how sizeable it can become. Time of Year Several of the bituminous-surfaced pavement treatments are Layout affected by ambient conditions at the time of placement. In particular, the cold-applied thin surfacings do not perform well The order and layout of the test sections over the length of when placed at low air or pavement temperatures, and chip a project should be done as randomly as possible. However, seals should never be placed on wet pavement when rainfall given that different treatments will be constructed at differ- is expected. Also, joint and crack sealants cannot be placed ent times, it is logical to construct all the treatments for a on damp surfaces. While in practice, preventive maintenance given timing cycle at one end of the project, and then proceed treatments are not always placed during optimal environmen- from that point for future construction of treatments at sub- tal conditions, it makes sense to try to construct the test sec- sequent timings. An example layout of test sections on a tions under favorable conditions. This is likely to mean a time multi-lane facility is shown in Figure D-1. For a two-lane facil- of the year when daytime temperatures are 16 °C (60 °F) and ity, test sections will have to be placed end-to-end. rising, freezing is not expected within 24 hours, and rainfall can be avoided. Crack sealants and joint resealing materials are usually placed on a dry pavement when temperatures are mod- Duration of Experiment erate, such as during late spring or late fall. The required period of time for monitoring treatments varies depending on the type of treatments. Less substantial Quality Control/Quality Assurance preventive maintenance treatments (such as fog seals or crack sealing) will require shorter evaluation periods then those The placement of a preventive maintenance treatment required for treatments such as microsurfacings or thin over- should not be approached any differently than other construc- lays. For most bituminous-surfaced sections, the monitoring tion undertaken by the agency. However, every effort should period is expected to range between 6 and 15 years. be made to ensure that treatments are properly constructed, TABLE D-4 Example factorial design table Timing of Application Year 0 Year 1 Year 2 Year 3 Year 4 Year 5 ... Year n Crack Sealing 2 sections 2 sections 2 sections 2 sections 2 sections 2 sections 2 sections Chip Seal 2 sections 2 sections 2 sections Fog Seal 2 sections 2 sections 2 sections 2 sections 2 sections 2 sections 2 sections 2 sections No Treatment 2 sections (Control)

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72 Two-Lane Roadways Section 1 Section 2 Section 3 Section 4 Section 5 Section 6 Section 7 Treatment B Treatment C Treatment A Treatment C Treatment A Treatment B Control WB Timing X Timing X Timing X Timing Y Timing Y Timing Y Treatment C Treatment A Treatment B Treatment B Treatment C Treatment A Section EB Timing Y Timing Y Timing Y Timing X Timing X Timing X Min 457 m Total Project Length Depending on Number of Treatment/Timing Combinations Four-Lane Roadways Section 14 Section 13 Section 12 Section 11 Section 10 Section 9 Section 8 WB Treatment A Treatment C Treatment B Control Treatment A Treatment B Treatment C WB Timing X Timing X Timing X Section Timing Y Timing Y Timing Y Section 1 Section 2 Section 3 Section 4 Section 5 Section 6 Section 7 EB Treatment B Control Treatment C Treatment A Treatment C Treatment A Treatment B EB Timing X Section Timing X Timing X Timing Y Timing Y Timing Y Min 457 m Total Project Length Depending on Number of Treatment/Timing Combinations Figure D-1. Example test section layouts for 2-lane and 4-lane roadways. and that subsequent performance is related to the treatment's ­ Treatments capabilities and not to construction defects. ­ Cleanliness It is recommended that the construction of all preventive · Materials maintenance treatments follow the agency's standard speci- ­ Constituents fications. In the absence of a standard specification, such as ­ Mix design when an experimental material is being evaluated, the sup- ­ Properties plier's or contractor's specifications should be followed. · Environmental conditions The agency should provide inspection services during con- ­ Temperature struction to monitor the placement of the test sections. The ­ Humidity inspector should be familiar with the project specifications ­ Rainfall and note the aspects of the project that affect performance, · Equipment calibration and performance including the following: · Treatment application rates · Surface preparation A standard form may be adapted to local conditions and ­ Defects used to record the results of the construction inspection. While ­ Overall surface condition the specifications may be fairly detailed, most preventive

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73 maintenance treatments are not complex, and required plans Manual Condition Surveys can typically be covered in a single 8 1/2 × 11 sheet of paper. It is recommended that manual condition surveys be con- ducted on all experimental sections within a project on at least Contractor Versus Agency Forces an annual basis. This can be done using an agency's distress manual or any similar manual that provides uniform defini- Some treatments are applied solely by specialty contrac- tions of distress type and severity (such as the LTPP distress tors and equipment (such as microsurfacing, diamond grind- manual). Recommended distress types that should be col- ing, and ultrathin surface treatments), while others may be lected are listed in Table D-5, but highway agencies may applied by agency forces or contractors (e.g., fog seals and include additional distresses as appropriate. A 150-m (500-ft) chip seals). There is no compelling reason to use contractors; segment located within the central part of each section and perhaps the best practice to follow is to apply the treatments away from the transition areas at either end should be selected in the same manner that the agency would normally follow. as the monitoring sample unit. Roughness Voiding Sections Roughness should be measured on all experimental sec- Sections that are improperly placed should be voided and tions within a project on an annual basis. The use of profil- removed from the experiment (i.e., not be further monitored). ing equipment is recommended, and the results should be Signs of improper placement include failure of the treatment expressed in terms of an International Roughness Index (IRI). to "stick," improper application rates, placement outside of ASTM E1926, Standard Practice for Computing Interna- the recommended environmental conditions (temperature tional Roughness Index of Roads from Longitudinal Profile and moisture, for example), and failures within the first year. Measurements, and AASHTO PP 37-00, Standard Practice for Quantifying Roughness of Pavements, provide details on these measurements. Section Marking It is extremely important to be able to locate the various Surface Friction pavement sections for many years after construction in order to (1) place the treatments in the right locations in subsequent If improving surface friction is a goal of placing the pre- years and (2) perform the necessary performance evalua- ventive maintenance treatments, then surface friction should tions. The use of permanent markers, such as surveying nails be monitored on an annual basis. Surface friction is generally driven into the pavement, is preferred over paint, which can measured using a locked-wheel skid trailer with either a ribbed wear off over time and under traffic. Often test sections are or smooth tire; however, the smooth tire correlates better with marked and remarked on the shoulder, but this may not be surface texture and wet-weather accidents. The output of the possible with certain surface treated or granular shoulders. If surface friction is expressed as either a skid number (SN) or the shoulders cannot be permanently marked with the test in terms of the International Friction Index (IFI). Applicable section limits, delineators should be placed adjacent to sec- specifications include ASTM E1960 and ASTM E274. tion limits at a safe distance to the side of the pavement. A map to the experimental section should also be devel- TABLE D-5 Recommended distress types to be oped. The map should show the locations of permanent land- collected marks (e.g. culverts, intersections, etc.) and offsets to the var- ious test sections. The map should be updated whenever new HMA and Bituminous PCC Pavements Pavements sections are constructed. Block Cracking Corner Breaks Fatigue Cracking Linear Cracking MONITORING ACTIVITIES Linear Cracking Joint Seal Damage Rutting Joint Spalling Regular monitoring of the experimental pavement sections is needed to assess the effects of the treatment and timing Bleeding Joint Faulting combinations. There are a wide variety of monitoring activ- Raveling Pumping ities that can be carried out; data collection efforts should Weathering (Oxidation) Blowups focus on collecting information that will facilitate the evalu- Polished Aggregate Patching ation of the treatment objectives (see Table D-1). The types Potholes of information that could be monitored are described in the Patching following subsections.

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74 Surface Texture · Bleeding--If localized, the section can continue to be monitored. If widespread, remove the section from the Closely related to surface friction is surface texture, which experiment. refers to the variations in a pavement surface that contribute · Rutting--It is unlikely that rutting is related to the per- to wet-weather friction, tire-pavement noise, splash and spray, formance of a preventive maintenance treatment; the rolling resistance, and tire wear. If determined to be appro- cause and extent of rutting should be evaluated. Rutting priate for a project, it is recommended that surface texture be that is prevalent throughout the project indicates that the measured on an annual basis using either the sand patch test section may not have been a good candidate for preven- or an outflow meter; alternatively, the use of high-speed, laser- tive maintenance, but rutting that is isolated to different based profiling devices could be used if available. The pre- sections may indicate a performance difference. As sec- ferred method of reporting surface texture is the mean tex- tions fail due to rutting they should be removed from the ture depth (MTD); if automated equipment is used the output experiment, but localized areas may be left in service. is an estimate of MTD, which is also acceptable. ASTM E965 · Raveling/Delamination--The cause of these distresses is the relevant specification. should be further investigated. If they occur in localized areas, then it may be possible to keep the section in ser- vice. Thin bituminous surfacings may be repaired if the Noise problem is localized and repaired soon after it occurs. If the problem is widespread or it is likely that the treat- Noise produced by the tire-pavement interaction of vehi- ment has failed, the section should be taken out of the cles may be a concern in urban areas. If controlling noise lev- experiment. els is one of the goals of an agency's preventive maintenance · Faulting/Pumping--These are likely signs that the pave- treatments, it should be monitored for consideration in the ment was not a good candidate for a preventive mainte- analysis. nance experiment; the cause and extent of faulting or pumping should be evaluated. Faulting and rutting that are prevalent throughout the project indicate that the Photo and Video Documentation section was probably not a good candidate for preven- tive maintenance, but faulting and rutting that are iso- As a final part of the data collection activities, it is recom- lated to different sections may indicate a performance mended that each test section be photographed and perhaps difference. As sections fail due to faulting or pumping videotaped during each annual inspection to provide a per- they should be removed from the experiment, but local- manent record of the treatment condition over time. ized areas may be left in service. These items are perceived to be the primary performance · Spalling--This should be further investigated to deter- indicators to be collected for the experimental pavement sec- mine whether the spalling is due to a materials/ tions. There may be additional indicators that highway agen- construction problem or to failure of the sealant system. cies may wish to include for specific treatments or to ensure · Joint or Crack Sealant Failure--If the sealant can be compatibility with other performance monitoring that they fixed shortly after failure, it should be fixed and the sec- may be conducting. tion monitoring continued. If the sealant has failed and cannot be repaired rapidly, the section should be taken out of the experiment. Treating Failure Eventually, the test sections will fail. If all goes well, fail- Ongoing Maintenance ure will occur at the end of the life of the treatment. However, Once all treatments are constructed and the pavement is as part of the design, the agency must be prepared to address opened to traffic, the issue of what maintenance is allowed sections that fail either due to a construction problem or due needs to be addressed; the agency's approach should be deter- to failure of the pavement. The following guidance may be mined ahead of time. It is recommended that the agency main- used to formulate a response to various failures. It is based tain the serviceability of the experimental section by main- on the premise that it is treatment timing that is being inves- taining the project with the same level of crack sealing and tigated in this experiment and not treatment performance. patching that would normally apply to the pavement. Therefore, certain treatment failures may be repaired to allow the section to stay in service. DATA ANALYSIS · Alligator cracking or other localized structural failures-- Fix pavement failures and continue to monitor the treat- After sufficient performance monitoring data is collected, ment if possible. the optimal timing of a given preventive maintenance treat-

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75 ment can be estimated using the spreadsheet-based analysis The treatment performance data collected as part of the tool. The analysis tool allows the calculation of the optimal plan is directly used to define these post-preventive mainte- time to apply a specific treatment by analyzing different treat- nance relationships associated with each unique combination ment application ages (timing scenarios) through the compu- of condition indicator and treatment application timing. tation of a benefit-cost (B/C) ratio associated with each selected timing scenario. The timing scenario with the largest computed B/C ratio identifies the optimal timing of those Database Development application ages investigated. The primary reason for implementing a plan is to collect To effectively use the provided analysis tool, it is recom- performance data that can be used to compute benefit values mended that a database be built to store the performance and associated with different timing scenarios for a specific pre- cost data that will be collected as part of the plan. The primary ventive maintenance treatment. Benefit is defined as any data types required by the analysis tool are the following: observed influence (mostly positive, but it could also be nega- tive) on any one or more condition indicators resulting from · Do-nothing expected condition indicator (perfor- the application of a preventive maintenance treatment. Using mance)--Before the influence of a preventive mainte- this definition, there could be many different types of benefit nance application can be analyzed, the analysis requires associated with a given application of the treatment (e.g., a baseline performance curve (or curves). The baseline applying a chip seal could result in benefits in the form of performance curve of interest for a particular condition improved friction, retarded oxidation, or reduced rutting). indicator is that performance curve (condition indicator Benefit for a given condition indicator is determined by versus time) that the agency would expect if only routine comparing the area associated with the condition indicator maintenance were conducted on the pavement (such curve without the application of preventive maintenance (i.e., curves are referred to as do-nothing performance curves). the do-nothing curve) with the area associated with the condi- The current methodology requires that the user define a tion indicator curve that is altered by the application of the pre- do-nothing performance curve for each of the condition ventive maintenance treatment. For condition indicators that indicators that are included in the analysis. The best decrease over time (e.g., serviceability, friction, or a typical source for this information is existing pavement man- composite index), it is the area under the curve that defines agement systems, although users without access to such benefit. For condition indicators that increase over time (e.g., curves can easily be walked through a process of approx- roughness, cracking, rutting, faulting, and spalling), it is the imation. Within the analysis tool, each do-nothing per- area above the curve that defines benefit. Figure D-2 illustrates formance relationship may be defined as (1) a known the resulting benefit area (AREABENEFIT) for a chosen condition equation (i.e., defined by an equation type and associ- indicator (e.g., serviceability [roughness]) when a treatment is ated coefficients) or (2) a series of performance versus applied at a pavement age of 12 years. age points through which a regression equation is fit. Do-nothing condition Application of PM activity indicator curve 5.0 Condition indicator curve after PM application Serviceability (roughness) 4.0 AREABENEFIT 3.0 Condition trigger level = 2.5 2.0 Expected do-nothing service life = 20 yrs 1.0 Expected service life with PM = 22 yr 5 10 15 20 Age, yrs Figure D-2. Illustration of benefit associated with the application of a preventive maintenance treatment.

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76 · Treatment performance relationships--In order to compared in the analysis (the analysis will identify the compute the benefit associated with a given performance most cost-effective application age from among those indicator, the performance monitoring data collected ages included in the analysis). under the plan is used to define the pavement's per- · Definition of do-nothing performance curves--Do- formance after a preventive maintenance treatment is nothing condition indicator relationships are entered (as applied. These relationships are used to compute the defined equations or as data for regression analysis) to benefit associated with each unique combination of con- define the baseline pavement performance without pre- dition indicator and application age. As with the do- ventive maintenance. nothing curves, each post-preventive maintenance rela- · Definition of post-preventive maintenance performance tionship may be defined by either defining a known curves--Performance data/relationships collected as equation or by entering a series of performance versus part of the plan are entered directly into the analysis age data. tool. · Treatment cost data--As part of implementing the plan, · Definition of costs--Inclusion of one of three costs types: detailed cost-related records should be kept during treat- (1) treatment construction costs, (2) work zone-related ment construction to document the treatment-related user delay costs, and (3) rehabilitation costs (applied at costs incurred by the agency. the end of a pavement's expected service life). · Benefit ranking factors--If multiple condition indica- tors are selected, an individual benefit is calculated for Refining Data for Analysis each and ranking factors are assigned as a means for dif- ferentially weighting the individual benefits associated Upon collecting and organizing all relative performance with the different condition indicators. and cost data, the user must refine the data to facilitate use in the analysis tool. The goal is to get one performance-versus- time relationship for each unique combination of condition The analysis will provide detailed information associated indicator and treatment application timing. Therefore, data with each application age. For each considered application from replicate experimental sections must be combined into age, the output data include a detailed benefit summary (both one representative performance relationship. This may be individual benefit values as well as a total combined benefit), accomplished by using engineering judgment or mathemati- a detailed cost summary, the computed B/C ratio, and the cal techniques such as averaging expected condition values at computed Effectiveness Index (EI). The timing scenario with each treatment age. Replicate cost data should be analyzed the largest computed B/C ratio (i.e., EI = 100) is the most using similar methods. While statistical analyses such as t-tests cost-effective application age. are most appropriate for analyzing whether replicate data are representative of the mean values, it is unlikely that there will be enough replicates to apply such tests. SUMMARY Conducting the Analysis The recommended plan describes an approach to help highway agencies collect the necessary data for determining In addition to defining the many performance relationships the optimal time to apply preventive maintenance treatments. (do-nothing and treatment-related) required by the analysis Successful implementation of this plan requires identifica- tool, many other project specific data elements must also be tion of the objectives of the preventive maintenance program defined prior to conducting the analysis. The following are and then selection of treatments and monitoring methods that the primary steps involved in the analysis: match these objectives. Recommendations are provided for site selection, site lay- · Condition indicator selection--Specification of one out, construction, and monitoring. The approach for analyz- or more condition indicators used to define pavement ing the collected data is described in this report; analysis can performance. be facilitated through the use of OPTime, the software tool · Preventive maintenance treatment selection--Selection developed in this project. It should be emphasized that this of one preventive maintenance treatment to be analyzed. plan is intended to identify the optimal time to perform a spe- · Selection of treatment application ages--Definition of cific preventive maintenance treatment, not to identify the best more than one treatment application age that will be preventive maintenance treatment.